The utilization of a relief or safety valve for venting excess pressure from a vessel or pipeline is well-known in the art. Typically, such a relief valve is spring or otherwise biased to a closed position and moves to an open position in response to such vessel or pipeline having an internal pressure greater than the predesignated release pressure of the relief valve. Relief valves installed in plants and the like need to be periodically checked to be certain that the valves are still properly operating. The valves can become corroded or, due to age or prior use, become totally or partially defective, which may prevent their operation when needed. One method for periodically testing a relief valve is to simply remove the relief valve from the pipeline or vessel and subject the relief valve to the pre-designed test pressure to determine whether or not the relief valve is properly functioning. One of the disadvantages of this type of test procedure is that it may be necessary to shut down operation of the vessel or pipeline in order to test the valve since it is actually removed for testing. A known way to avoid the removal of the relief valve for testing is to permanently mount an intermediate block valve between the relief valve and the pipeline or vessel. When it is necessary to test the relief valve, the block valve is closed and the relief valve is tested by the application of pressure through the closed block valve to the relief valve. This procedure has the disadvantage of preventing the operation of the relief valve during the test. If an emergency arises during the test period while the block valve is closed, the ability to release dangerous pressure levels from the pipeline or vessel is unavailable just when it is most needed. Another disadvantage of the use of block valves is the possibility of inadvertent closing of the block valve by an operator while performing operator duties.